PMC6178136_01
Histologic features of Mammary Analog Secretory Carcinoma of Thyroid (a). The origin of this unusual tumor is unknown but may be from incidental intrathyroidal salivary gland rests as seen in this normal thyroid (not from the patient reported) (b). The thyroid tumor in the case described is an infiltrative tumor composed of solid sheets and nests of epithelial cells in a fibrous stroma. The surrounding thyroid exhibits chronic lymphocytic thyroiditis (c). The solid sheets were punctuated by small cribriform areas and microcysts with pseudopapillae and a few true papillae with fibrovascular cores (d). The homogeneous tumor cells had abundant cytoplasm and monotonous round nuclei with clear nucleoplasm and conspicuous large nucleoli but no indentations or inclusions (e). There was extrathyroidal extension into surrounding skeletal muscle (f). In one area of the tumor there was a small 0.2 cm focus of classical papillary microcarcinoma.
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F1
The tumor was composed of solid sheets and nests in a fibrovascular stroma (Figure 1b) with cribriform areas, microcysts, cleft-like structures, and focal pseudopapillae with a few true papillae (Figure 1c). The tumor cells were relatively homogeneous with abundant eosinophilic cytoplasm and monotonous round nuclei with clear nucleoplasm and conspicuous large nucleoli but no indentations or inclusions (Figure 1d). There was frank extrathyroidal extension into surrounding skeletal muscle (Figure 1e). In one area of the tumor there was a small 0.2 cm focus of classical papillary microcarcinoma with the distinctive features of that entity that were clearly different from the rest of the lesion (Figure 1f).
Immunohistochemical features of Mammary Analog Secretory Carcinoma of Thyroid (a). The tumor cells exhibit diffuse positivity for monoclonal PAX-8 that is much weaker than in the surrounding thyroid (b). There is very focal positivity for TTF-1 (clone: SPT24); some of the stained cells might be entrapped follicular epithelial cells (c). The tumor cells are completely negative for thyroglobulin (d). The tumor exhibits strong diffuse positivity for cytokeratin 19 (e). Staining for CEA with a polyclonal antiserum yields diffuse reactivity, however a monoclonal CEA antibody resulted in a completely negative stain (f). Tumor cells are positive for gross cystic disease fluid protein-15 (g). Scattered tumor cells express p63 (h). Dendritic type cells that are strongly positive for S100 protein are distributed throughout the tumor (i). Beta-catenin staining is intact at the cell membrane and there is no nuclear translocation (j). Positivity for E-cadherin is retained at the cell borders.
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F2
SPT24) was only focal and weak (Figure 2b) and thyroglobulin staining was completely negative (Figure 2c). Stains for Cytokeratin 7 and Cytokeratin 19 (Figure 2d) were diffusely positive but Cytokeratin 5 was only focally expressed. Although polyclonal CEA was positive (Figure 2e), monoclonal CEA was negative, as was synaptophysin and chromogranin-A. Scattered tumor cells were positive for gross cystic disease fluid protein-15 (GCDFP-15) (Figure 2f), some stained for p63 (Figure 2g) and stellate cells were identified by localization of S100 protein (Figure 2h). Beta-catenin (Figure 2i) and E-cadherin (Figure 2j) positivity was intact at the tumor cell membrane and there was no nuclear translocation.