2021 Volume 20 Issue 1 Pages 24-29
A 77-year-oldfemale presentedwith multiple subcutaneous nodules on the abdomen for a month. Computedtomography of the chest andabdomen demonstratedmultiple tumors in the lung andliver. A clinical investigation revealed25 mm-sizedsubcutaneous nodules respectively on the epigastric region andthe right lower abdomen, accompaniedby multiple, small, fingertip-sizedsubcutaneous nodules on the chest and abdomen. A biopsied specimen demonstrated a relatively welldemarcated, irregularly-shaped basophilic nodule in the subcutaneous tissue. Tumor cells had roundto oval, hyperchromatic, atypical nuclei, anda faint cytoplasm with high nucleo-cytoplasmic ratio. A lot of mitoses could be detected. Indian filing could be seen partially. Immunohistochemically, tumor cells were positive for CK7, CD56, synaptophysin, chromogranin A, andthyroid transcription factor-1 (TTF-1), andwere negative for CK20. Positron emission tomography/computedtomography (PET/CT) demonstratedan abnormal uptake of FDG in the subcutaneous tissue, the liver, the upper lobe andhilum of the left lung, mediastinal andbilateral axillary lymph nodes, and adrenal gland. Metastatic carcinoma of the skin from lung small cell carcinoma could be diagnosed definitely. Several transcription factors have been reportedto be useful as specific markers in a variety of internal carcinomas. In the present case, the expression of TTF-1 enabled the diagnosis of lung small cell carcinoma. A skin biopsy is a useful tool in investigating the origin of metastatic carcinomas of the skin, leading to the choice of appropriate treatment. Skin Research, 20 : 24-29, 2021
