PMC8116143_01
Representative hematoxylin and eosin images (a-f) revealing tumor composed of variably sized irregular solid nests of basaloid cells and anastomosing tubules with desmoplastic stroma (a, 100x magnification). Focal peripheral palisading with peritumoral clefting (b, 100x magnification), comedonecrosis (c, 200x magnification), and invasion into the bladder neck (d, 100x magnification) was noted. Cribriform architecture with eosinophilic hyaline material in the lumen resembling adenoid cystic carcinoma (e, 200x magnification) and perineural invasion (f, 200x magnification) were also present.
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Microscopically, the prostate chips showed variable sized medium to large irregular shaped basaloid nests (Figure 1(a)). Focal areas with peripheral palisading (Figure 1(b)), anastomosing nests (Figure 1(a)), and tubules with necrosis were seen (Figure 1(c)). Some of the nests were present in between benign prostate glands and focally extended between thick muscle bundles suggestive of invasion into the bladder neck (Figure 1(d)). Adenoid cystic-like pattern with cribriform architecture, intra-luminal eosinophilic, hyaline basement membrane-like material (Figure 1(e)), and perineural invasion (Figure 1(f)) was also present. Focal stromal desmoplastic response was observed (Figure 1(a)).
Immunohistochemistry and cytogenetics studies support the diagnosis of prostatic BCC. The tumor cells revealed strong and diffuse reactivity for Bcl-2 (a, 200x magnification), variable multilayer reactivity for basal markers such as p63 and HMWCK (b, 200x magnification). Ki-67 staining showed high proliferation of >30% (c, 200x magnification). The tumor was negative for NKX3.1 (d, 200x magnification) and racemase (b, 200x magnification). Break-apart FISH for MYB image did not show separation of 5'MYB and 3'MYB (E).
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Immunohistochemically, the tumor revealed strong and diffuse reactivity for cytokeratin (CK) 7 and Bcl-2 (Figure 2(a)) and weak focal staining for GATA3. Variable multilayer reactivity for basal markers such as p63 and high molecular weight cytokeratin (HMWCK) was observed (Figure 2(b)). Ki-67 staining showed high proliferation (>30%, Figure 2(c)). The tumor was negative for CK20, NKX3.1 (Figure 2(d)), racemase (Figure 2(b)), synaptophysin, chromogranin, androgen receptor (AR), and HER2 (Table 1). ACC-like pattern, MYB break-apart was negative/not detected and all tumor cells have two fusion fluorescence signals (Figure 2(e)). Additional FISH studies using two fusion probes for MYB-NFIB and MYBL1-NFIB fusions also turned out to be negative.