Sclerosing Polycystic Adenosis Arising in the Parotid Gland Without PI3K Pathway Mutations

Abstract

A 15-year-old old Japanese male with a 2-month history of swelling of his left subauricular area was admitted to our department. A thumb-sized, hard mass with mild tenderness was palpated on the left parotid gland. Ultrasonography revealed a well-circumscribed, hypoechoic mass exhibiting heterogeneity in the left parotid gland measuring 1.7 × 1.5 × 1.3 cm. Computed tomography scan revealed a well-circumscribed, solid mass exhibiting slight peripheral enhancement in the left parotid gland. Magnetic resonance imaging revealed a hypointense mass in the left parotid gland on both T1-and T2-weighted images. Clinicoradiologic findings suggested a benign or low-grade malignant parotid tumor. The patient underwent left superficial parotidectomy with adequate safety margins. The facial nerve was identified and preserved. Neither facial paralysis nor tumor recurrence was observed as of 1 year postoperatively. Histologically, the nodule consisted of a vaguely nodular arrangement of variably sized ducts and acini in a hyalinized fibrous background with focal myxoid changes. The ductal/ acinar component exhibited a bilayered arrangement of cuboidal luminal and flattened abluminal cells exhibiting a variety of epithelial proliferative patterns, including micropapillary and cribriform. Areas of oncocyte-like changes with intracellular coarse eosinophilic granules, apocrine-like feature, foamy/vacuolated changes, and clear cells were noted in the proliferating epithelium. Immunohistologically, the luminal cells were positive for gross cystic disease fluid protein-15. The Ki-67 labeling index was 2-3%. The histologic features and immunohistologic profile were consistent with sclerosing polycystic adenosis. Targeted next-generation sequencing of 160 cancer-related genes using the surgical specimen revealed no mutations, including known significant mutations in PTEN, PIK3CA, or PIK3R1.

Clinicopathological profile of sclerosing polycystic adenoma/adenosis: A systematic review

“…Monoclonality of the cells was revealed in all female patients investigated using a PCR‐based analysis of patterns of X chromosome inactivation using human androgen receptor (HUMARA) locus 3 . In contrast, one study did not find any mutation including PTEN , PIK3CA , or PIK3R1 12 . ETV6 FISH was negative for gene rearrangement 13 …”

“…The diagnostic of SPA by fine‐needle aspiration cytology (FNAC) is difficult considering the variety of cytologic characteristics. No study could diagnose SPA only with FNAC 12 . In several cases, the diagnosis was given as pleomorphic adenomas or other benign lesions 12,14–22 .…”

“…No study could diagnose SPA only with FNAC 12 . In several cases, the diagnosis was given as pleomorphic adenomas or other benign lesions 12,14–22 . Nevertheless, FNAC proved to be beneficial because it ruled out the presence of a malignancy in most of the cases.…”

“…Large acinar cells with an abundance of eosinophilic cytoplasmic granules are another feature found in SPA. The stroma is densely collagenized with a chronic inflammatory infiltrate 12 …”

“…Ductal cells exhibit strong immunohistochemical positivity for cytokeratin (AE1/AE3, CAM5.2) and EMA 12 . Both myoepithelial and ductal cells express the S‐100 protein positively 12 . GCDFP‐15 was highly positive in acinar cells 12 .…”