UNASSIGNED: A 55-year-old male patient developed a mass in the left inguinal area with left lower limb swelling and first visited a local hospital 3 months earlier because of unrelieved pain. An MRI scan suggested left suprapubic branch and left acetabular bone destruction, abnormal soft tissue signals within the iliopsoas muscle of the anterior edge of the left iliac bone, and enlarged lymph nodes in the left iliac fossa and left inguinal region. The patient subsequently underwent left pelvic lesion open biopsy and inguinal lymph node resection biopsy. According to pathological reports, the left inguinal mass was considered to be a malignant tumor of cutaneous accessory origin (pilomatrix carcinoma) with extensive vitreous changes. The suprapupubis branch mass was considered to be a bone metastatic pilomatrix carcinoma. Immunohistochemistry (IHC) revealed a PDL1 combined positive score (CPS) of 8. DNA next-generation sequencing (NGS) showed CDKN2A L65Rfs*53 mutation. The patient received three cycles of gemcitabine and nedaplatin. However, the lesion progressed.
UNASSIGNED: Chemotherapy is not effective for treating pilomatrix carcinoma. PDL1 antibodies and CDK4/6 inhibitors might be treatment options for pilomatrix carcinoma.

Pilomatrix carcinoma (PC) is a rare skin adnexal neoplasm derived from piliferous follicles, usually occurring in the head and neck region. An optimal treatment for PC has not yet been established, while surgery with wide margins is recommended, with radiation therapy (RT) and chemotherapy improving the curative effect. Location of this tumor in the breast is exceedingly rare, especially for a male. We now report an unusual case of a 53-year-old male who presented with 2 palpable masses in the right breast, which had been removed surgically about 4 and a half years prior, but recurred after 7 months. Ultrasonography revealed 2 irregular low-echo masses with a well-defined boundary, and computed tomography (CT) showed 2 soft tissue masses in subcutaneous tissue of the right breast. The tumors were completely removed without RT and chemotherapy. After about 4 years\' follow-up, the patient remains free of local recurrence and metastasis. To the best of our knowledge, only 2 cases of PC in the breast region have been reported, but were female.

Pilomatrix carcinoma (PC) is a rare neoplasm, particularly in the parotid region. Thus, it is easily misdiagnosed and an optimal treatment regimen has not yet been established. The present study reports the case of a 43-year-old female who presented with a PC of the parotid region and reviews the associated published literature. The patient underwent three surgical excisions prior to the tumor being completely removed, and was misdiagnosed four times prior to the correct diagnosis. Once the tumor was completely removed, the patient received radiation therapy (RT). At the 2-year follow-up, the patient remained free of local recurrence and metastasis. To the best of our knowledge, only 3 cases of PC on the parotid region have been reported. Although an optimal treatment regimen has not been established, surgery with wide margins is recommended, with RT and chemotherapy producing mixed results.