• Rare tumor usually involving the parotid, which is characterized by intracystic / intraductal proliferations of neoplastic epithelial cells
• Exists in at least 3 variations, each with unique histologic, immunophenotypic and molecular features
• Relationship to salivary duct carcinoma is unclear

• Resembles ductal carcinoma in situ of the breast, with cribriform, micropapillary, solid, comedo or clinging patterns (Cancer 1996;78:958)
• At least 3 variants
  • Intercalated duct-like (most common) (Am J Surg Pathol 2018;42:442)
  • Apocrine (Am J Surg Pathol 2006;30:1014)
  • Mixed / hybrid
  • Possibly oncocytic but may be a variant of intercalated duct type (Histopathology 2018;73:314)
• Diagnosis requires thorough sampling to rule out invasion or presence of a myoepithelial layer by immunohistochemistry
• No purely intraductal carcinomas have definitively recurred or distantly metastasized

• Low grade cribriform cystadenocarcinoma
• Low grade intraductal carcinoma
• Low grade salivary duct carcinoma
• Salivary duct carcinoma in situ

• Rare, with an estimated 93 cases reported (APMIS 2020;128:191)
• Affects a wide age range; F:M = 1.5:1 (Head Neck Pathol 2013;7:S59)

• Must exclude invasion by thorough sampling or presence of a myoepithelial layer by immunohistochemistry (Am J Surg Pathol 2004;28:266)

• No purely intraductal carcinomas have definitively recurred or distantly metastasized (Head Neck Pathol 2013;7:S59)
• Few show invasive growth, several with widespread invasion (Am J Surg Pathol 2019;43:1303)

Contributed by Kim A. Ely, M.D.

Which of the following is true regarding this variant of intraductal carcinoma with the following immunophenotype: S100 and SOX10+; AR-?

1. It is associated with HRAS and PIK3CA hotspot mutations
2. It is the most common variant
3. It is the type most likely to exhibit high grade nuclear features
4. It is usually GCDFP-15+

B. It is the most common variant

The photomicrograph shows an intraductal proliferation of bland appearing cuboidal cells arranged in cribriform and clinging patterns. Nuclei are small and oval with a dispersed chromatin distribution. Immunohistochemical studies were positive for S100 and SOX10, while negative for AR (androgen receptor) and GCDFP-15. This constellation of findings is characteristic of the intercalated duct-like variant, which is the most common of the variants. It is frequently associated with RET fusions, commonly NCOA4-RET. HRAS and PIK3CA hotspot mutations are usually seen in the apocrine variant, which is the form more likely to exhibit higher grade atypia. It has the following immunophenotype: S100-, SOX10-, AR+ and GCDFP-15+. This staining pattern is similar to that of salivary duct carcinoma, leading to some to believe that apocrine intraductal carcinoma may be a precursor to conventional salivary duct carcinoma.

Comment Here

Reference: Intraductal carcinoma

Which of the following is true regarding intraductal carcinoma?

1. A diagnosis can be made on core biopsy
2. Has a marked predilection for women
3. It is most common in the submandibular gland followed by the parotid
4. No purely intraductal carcinomas have definitively recurred or distantly metastasized

D. No purely intraductal carcinomas have definitively recurred or distantly metastasized.

Intraductal carcinoma involves the parotid (84.6%), intraparotid lymph nodes (5.1%), accessory parotid gland (2.6%), submandibular gland (2.6%) and minor salivary glands (5.1%). Women and men are almost equally affected, with a female to male ratio of 1.5:1. According to the diagnostic criteria outlined by Cheuk et al., a diagnosis of intraductal carcinoma can be made once an invasive component is excluded. This requires thorough sampling or the demonstration of a myoepithelial layer around the epithelial nest by immunohistochemistry. This is more confidently accomplished on an excisional specimen. When confined by a myoepithelial cell layer, no intraductal (or in situ) carcinomas have definitively recurred or distantly metastasized.

Comment Here

Reference: Intraductal carcinoma