UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington D.C. 20549

FORM 10-D

ASSET-BACKED ISSUER
DISTRIBUTION REPORT PURSUANT TO SECTION 13 OR 15(d) OF
THE SECURITIES EXCHANGE ACT OF 1934

For the monthly distribution period from:
SeptemberOctober 1311, 2025 to OctoberNovember 1013, 2025

Commission File Number of issuing entity: 333-193376-19
Central Index Key Number of issuing entity: 0001643293

COMM 2015-LC21 Mortgage Trust
(Exact name of issuing entity as specified in its charter)

Commission File Number of depositor:  333-193376
Central Index Key Number of depositor: 0001013454

Deutsche Mortgage & Asset Receiving Corporation
(Exact name of depositor as specified in its charter)

Central Index Key Number of sponsor (if applicable): 0001541294
German American Capital Corporation
(Exact name of sponsor as specified in its charter)

Central Index Key Number of sponsor (if applicable): 0001558761
Cantor Commercial Real Estate Lending, L.P.
(Exact name of sponsor as specified in its charter)

Central Index Key Number of sponsor (if applicable): 0001541468
Ladder Capital Finance LLC
(Exact name of sponsor as specified in its charter)

Central Index Key Number of sponsor (if applicable): 0001089877
KeyBank National Association
(Exact name of sponsor as specified in its charter)

Lainie Kaye (212) 250-2500
(Name and telephone number, including area code, of the person to
contact in connection with this filing)

New York
(State or other jurisdiction of incorporation or organization
of the issuing entity)

Lower Tier Remic 47-4300612
Upper Tier Remic 47-4322711
Grantor Trust 47-7135776
(I.R.S. Employer Identification No.)

c/o Deutsche Bank Trust Company Americas as Certificate Administrator
1761 East St. Andrew Place, Santa Ana CA
(Address of principal executive offices of the issuing entity)

92705
(Zip Code)

(212) 250-2500
(Telephone number, including area code)

NONE
(Former name, former address, if changed since last report)

Registered / reporting pursuant to (check one)
Title of Class  Section 12(b)  Section 12(g)  Section 15(d)  Name of Exchange
(if Section 12(b))
Class A-1           [ ]             [ ]             [X]        Not Applicable
Class A-2           [ ]             [ ]             [X]        Not Applicable
Class A-SB          [ ]             [ ]             [X]        Not Applicable
Class A-3           [ ]             [ ]             [X]        Not Applicable
Class A-4           [ ]             [ ]             [X]        Not Applicable
Class X-A           [ ]             [ ]             [X]        Not Applicable
Class A-M           [ ]             [ ]             [X]        Not Applicable
Class B             [ ]             [ ]             [X]        Not Applicable
Class C             [ ]             [ ]             [X]        Not Applicable
Class D             [ ]             [ ]             [X]        Not Applicable

Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act
of 1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to
such filing requirements for the past 90 days. Yes _X_   No ____


Part I - DISTRIBUTION INFORMATION

Item 1.  Distribution and Pool Performance Information.
On  OctoberNovember 1013, 2025 a distribution was made to holders of the
certificates issued by COMM 2015-LC21 Mortgage Trust.  The
distribution report is attached as Exhibit 99.1 to this Form 10-D.

During the distribution period from SeptemberOctober 1311, 2025 to OctoberNovember 1013, 2025
no assets securitized by Deutsche Mortgage & Asset Receiving
Corporation (the "Depositor") and held by COMM 2015-LC21 Mortgage
Trust were the subject of a demand to repurchase or replace for breach
of the representations and warranties contained in the underlying
transaction documents.

The Depositor filed a Form ABS-15G pursuant to Rule 15Ga-1 under the
Securities Exchange Act of 1934 on February 13, 2025.  The CIK number
of the Depositor is 0001013454.

German American Capital Corporation ("GACC"), one of the sponsors and
mortgage loan sellers, filed a Form ABS-15G pursuant to Rule 15Ga-1
under the Securities Exchange Act of 1934 on February 13, 2025.  The
CIK number of GACC is 0001541294.

Cantor Commercial Real Estate Lending, L.P. ("CCRE"), one of the
sponsors and mortgage loan sellers, filed a Form ABS-15G pursuant to
Rule 15Ga-1 under the Securities Exchange Act of 1934 on
October 17, 2025.  The CIK number for CCRE is 0001558761.

Ladder Capital Finance LLC ("Ladder"), one of the sponsors and mortgage
loan sellers, filed a Form ABS-15G pursuant to Rule 15Ga-1 under the
Securities Exchange Act of 1934 on February 14, 2025.  The CIK number
of Ladder is 0001541468.

KeyBank National Association ("KeyBank"), one of the sponsors and
mortgage loan sellers, filed a Form ABS-15G pursuant
to Rule 15Ga-1 under the Securities Exchange Act of 1934 on
August 14, 2025.  The CIK number of KeyBank is 0001089877.


Part II - OTHER INFORMATION

Item 2. Legal Proceedings.
Disclosure from Deutsche Bank Trust Company Americas, as certificate
administrator and as custodian:

In 2014 and 2015, several investors sued several trustees of residential
mortgage-backed securities ("RMBS") trusts, including Deutsche Bank Trust
Company Americas ("DBTCA"), concerning the trustees' administration of
RMBS trusts. These cases generally alleged that the RMBS trustees failed
to perform purported duties, as trustees for private-label RMBS trusts,
to enforce breaches of representations and warranties as to mortgage loans
held by the trusts and to enforce breaches by servicers of their mortgage
loan servicing obligations for the trusts. Investors have sued DBTCA in
six of these cases. DBTCA has settled two cases brought by funds managed
by Blackrock Advisors, LLC, PIMCO-Advisors, L.P. and others; and obtained
summary judgment in one case, brought by certain special purpose entities
including Phoenix Light SF Limited. In addition, the two cases described
below remain active.

On November 30, 2017, DBTCA was added as a defendant to a case brought by
Commerzbank AG ("Commerzbank") in the U.S. District Court for the Southern
District of New York, in which Commerzbank previously alleged incorrectly
that Deutsche Bank National Trust Company ("DBNTC") served as trustee for
all 50 of the trusts at issue. On November 30, 2017, Commerzbank filed a
second amended complaint that names DBTCA as a defendant in addition to
DBNTC. DBTCA serves as trustee for 1 of the 50 trusts at issue. DBNTC
serves as trustee for the other 49 trusts at issue. Commerzbank's second
amended complaint brings claims for violation of the U.S. Trust Indenture
Act of 1939 ("TIA"); breach of contract; breach of fiduciary duty;
negligence; violation of the New York Streit Act ("Streit Act"); and
breach of the covenant of good faith. However, in the second amended
complaint, Commerzbank acknowledges that, before DBTCA was added to the
case, the court dismissed Commerzbank's TIA claims for the trusts governed
by pooling and servicing agreements, as well as its Streit Act claims and
claims for breach of the covenant of good faith, and Commerzbank only
includes these claims to preserve any rights on appeal. The second amended
complaint alleges that DBNTC and DBTCA caused Commerzbank to suffer
"hundreds of millions of dollars in losses," but the complaint does not
include a demand for money damages in a sum certain. On January 29, 2018,
DBNTC and DBTCA filed an answer to the second amended complaint. On
December 7, 2018, DBNTC and DBTCA filed a motion for summary judgment.
Also on December 7, 2018, Commerzbank, jointly with the Phoenix Light
plaintiffs, filed a motion for partial summary judgment. On February 8,
2022, the court issued an order in which it granted in part DBNTC and
DBTCA's motion for summary judgment and denied plaintiffs' motion for
partial summary judgment. As a result of that order, many of plaintiffs'
claims and theories were dismissed with prejudice. On September 26, 2024,
DBNTC and DBTCA filed a motion for summary judgment, which has been fully
briefed.

On December 30, 2015, IKB International, S.A. in Liquidation and IKB
Deutsche Industriebank A.G. (collectively, "IKB"), as an investor in
37 RMBS trusts, filed a summons with notice in the Supreme Court of the
State of New York, New York County, against DBNTC and DBTCA as trustees
of the trusts. On May 27, 2016, IKB served its complaint asserting claims
for breach of contract, breach of fiduciary duty, breach of duty to
avoid conflicts of interest, violation of the Streit Act, violation of
the TIA, violation of Regulation AB, and violation of Section 9 of the
Uniform Commercial Code. IKB alleges that DBNTC and DBTCA are liable
for over U.S. $268 million in damages. On October 5, 2016, DBNTC and
DBTCA, together with several other trustees defending lawsuits by IKB,
filed a joint motion to dismiss. On January 6, 2017, IKB filed a notice
of discontinuance, voluntarily dismissing with prejudice all claims as to
three trusts. On June 20, 2017, the parties filed a stipulation,
voluntarily dismissing with prejudice all claims as to four additional
trusts. On January 27, 2021, the court granted in part and denied in
part DBNTC and DBTCA's motion to dismiss. The court granted the motion to
dismiss with respect to IKB's claims for violations of the Streit Act,
Regulation AB, and Section 9 of the Uniform Commercial Code, as well as
certain aspects of IKB's claims for breach of contract, breach of fiduciary
duty, and violation of the TIA. The court denied the remainder of the
motion to dismiss. IKB's remaining claims for breach of contract, breach
of fiduciary duty, breach of duty to avoid conflicts of interest, and
violation of the TIA will proceed. On May 10, 2021, DBNTC and DBTCA filed
a notice of appeal with the New York Supreme Court Appellate Division,
First Department, regarding certain aspects of the court's order on the
motion to dismiss. On May 20, 2021, IKB filed a notice of cross appeal
with respect to other aspects of that order. On August 30, 2022, the New
York Supreme Court, Appellate Division, First Department affirmed in part
and reversed in part the court's order on the motion to dismiss. After
DBNTC and DBTCA appealed the First Department's decision, on June 15, 2023,
the New York Court of Appeals reversed the First Department's decision in
part, dismissing certain additional contract claims, as well as IKB's
claims for breach of fiduciary duty and breach of duty to avoid conflicts
of interest. On June 2, 2021, IKB filed a motion for re-argument regarding
certain aspects of the court's order on the motion to dismiss, which the
court denied on August 3, 2021. On May 13, 2021, DBNTC and DBTCA filed an
answer to the complaint. On October 28, 2021, the parties filed a
stipulation, voluntarily dismissing with prejudice all claims as to seven
additional trusts. On December 29, 2021, the parties filed a stipulation,
voluntarily dismissing with prejudice all claims as to one additional trust.
On April 22, 2022, the parties filed a stipulation, voluntarily dismissing
with prejudice all claims as to 17 certificates at issue, including all
claims as to 5 trusts. On February 28, 2023, the parties filed a
stipulation, voluntarily dismissing with prejudice all claims as to two
trusts, leaving 15 trusts at issue. On November 21, 2023, the parties filed
a stipulation, voluntarily dismissing with prejudice all claims as to three
trusts, leaving 12 trusts at issue. On November 14, 2024, DBNTC and DBTCA
filed a motion for summary judgment. Also on November 14, 2024, IKB filed
a motion for partial summary judgment. On August 11, 2025, the court
granted in part and denied certain aspects of both motions. On October 20,
2025, the court resolved the remainder of both motions and dismissed
certain additional claims.

It is DBTCA's belief that it has no pending legal proceedings (including,
based on DBTCA's present evaluation, the litigation disclosed in the
foregoing paragraphs) that would materially affect its ability to
perform its duties under the Pooling and Servicing Agreement for this
transaction.

Item 10. Exhibits.
(a) The following is a list of documents filed as part
    of this Report on Form 10-D:

(99.1)   Monthly Report distributed to holders of the
         certificates issued by COMM 2015-LC21 Mortgage Trust,
         relating to the OctoberNovember 1013, 2025 distribution.

(b) The exhibits required to be filed by the Registrant
    pursuant to this Form are listed above.


SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.

Deutsche Mortgage & Asset Receiving Corporation
(Depositor)


/s/ R. Chris Jones
Name:  R. Chris Jones
Title: Managing Director


/s/ Matt Smith
Name:  Matt Smith
Title: Director



Date:    OctoberNovember 2019, 2025
Filing Compare · COMM 2015-LC21 Mortgage Trust
