MUCINOUS CARCINOMA

MUCINOUS CARCINOMA

• Synonyms  – Mucoid carcinoma, Colloid carcinoma, Gelatinous carcinoma
• It is an invasive ductal carcinoma characterized by neoplastic cells floating within extracellular mucins. It is carcinoma with low malignant potential.
• Mucinous carcinomas are diagnosed as pure mucinous carcinoma when atleast 90% of total neoplastic area exhibits neoplastic cells floating within extracellular mucin, mixed when 10 to 90% of neoplastic lesion is mucinous and remaining component is constituted by ordinary ductal carcinoma NOS. if less than 10% is mucinous area the tumor is classified depending upon the type of invasive component
• Clinical feature
  • Incidence ranges from 0.8 – 5.3 of all breast carcinomas
  •   Mostly affects females ( rarely affects males)
  • Occurs at older age than ordinary invasive carcinoma
• Gross findings – Tumor has well circumscribed pushing border.Cut surface is pink gelatinous with areas of hemorrhages
• Microscopic findings
  • Mucinous carcinoma is subdivided into two subtypes with intermediate type AB. Subtyping has no prognostic importance but it indicates histogenesis
  •  Type A mucinous carcinoma –It has greater content of mucin, ranging from 60 to 90% . Neoplastic cells are arranged in rings, festoons and ribbons. Nuclei of the tumor cells are irregular occasionally giant bilobated (grade 1-2) nucleoli are small and mitosis are not frequent. Cytoplasm is eosinophilic and hyaline. No intracytoplasmic mucin is noted.
  • Type B mucinous carcinoma –  Mucin content in these tumors ranges from 33 to 75%. Neoplastic cells are arranged in rounded, ovoid or elongated blunt edged clumps, either isolated or confluent in anastomosing sheets floating within mucous. Nuclei are regular (usually grade 1) ranging from round to ovoid with evident nucleoli. The cytoplasm is eosinophilic and finely granular. Intracytoplasmic lumens are seen .
  • Type AB mucinous carcinoma – In these tumors both subtypes are seen close to one another
• Differential diagnosis
  • Fibroadenoma with myxoid stroma
  • Mucocele – like tumor
  • Mucinous cystadenocarcinoma
  • Matrix producing carcinoma
  • Squamous cell carcinoma with prominent myxoid stroma