ONCOCYTOMA

Comprise 2% of salivary gland neoplasm
Encapsulated tumor consisting of exclusively oncocytes without any features of other salivary gland tumors
Oncocytosis – diffuse oncocytic metaplasia of ductal cells accompanied by loss of acinar units with preservation of lobular architecture
Multifocal nodular oncocytic hyperplasia
- characterised by multiple non-encapsulated nodules formed by the proliferation of oncocytes
- features favouring oncocytic hyperplasia are
  - multiple nodules rather than single nodule as in oncocytoma
  - lack of capsule
  - Nodules with lobular configuration which gradualy merge into normal ducts and acini
  - focal clear cell change
Clinical features
- presents as painless swelling
- Site – most common in parotid but can occur in submandibular gland and minor salivary glands also
- Age – elderly age group (6th to 7th decades)
- Gender – without sex predilection
- Risk factor – exposure to radiation to the head and neck region
Pathological features
- Gross – encapsulated solid lesion with mahogany brown colour (reddish brown)
- Microscopy –
  - Tumor cells arranged in trabecular, sheets, nodules, rarely glandular pattern which are separated by scanty loose vascularized stroma
  - microcyst formations are seen
  - Nodules of ocncocytes are surrounded by basal cells which are positive for p63 and CK5/6
  - Oncocytes are cuboidal or polygonal with abundant granular eosinophilic cytoplasm and with central round nuclei and distant nucleoli. special stains like PTAH can be used to high light mitochondria
  - psammoma bodies, squamous cells, sebaceous and goblet cells may be present focally
  - Tyrosine rich crystals which are eosinophilic needle shaped or plate like are present either with in oncocytic cells or extracellularly
  - Areas of infarction and squamous metaplasia with atypical nuclei can also be seen
Variant
- Clear cell oncocytoma
  - 11% of oncocytomas has clear cells as predominant component
  - shows female predilection
  - clear cytoplasm is due to glycogen accumulation
  - These tumors have high frequency of bilaterality and recurrence
Differential diagnosis
- Warthin tumor – Oncocytoma with lymphocytic infiltrate in stroma
- Acinic cell carcinoma – similar cell arrangement and granularity in the cytoplasm but nuclei is peripherally located, in contrast to centrally located nuclei in oncocytoma

ONCOCYTOMA

Comprise 2% of salivary gland neoplasm

Encapsulated tumor consisting of exclusively oncocytes without any features of other salivary gland tumors

Oncocytosis – diffuse oncocytic metaplasia of ductal cells accompanied by loss of acinar units with preservation of lobular architecture

Multifocal nodular oncocytic hyperplasia

characterised by multiple non-encapsulated nodules formed by the proliferation of oncocytes

features favouring oncocytic hyperplasia are

multiple nodules rather than single nodule as in oncocytoma

lack of capsule

Nodules with lobular configuration which gradualy merge into normal ducts and acini

focal clear cell change

Clinical features

presents as painless swelling

Site – most common in parotid but can occur in submandibular gland and minor salivary glands also

Age – elderly age group (6th to 7th decades)

Gender – without sex predilection

Risk factor – exposure to radiation to the head and neck region

Pathological features

Gross – encapsulated solid lesion with mahogany brown colour (reddish brown)

Microscopy –

Tumor cells arranged in trabecular, sheets, nodules, rarely glandular pattern which are separated by scanty loose vascularized stroma

microcyst formations are seen

Nodules of ocncocytes are surrounded by basal cells which are positive for p63 and CK5/6

Oncocytes are cuboidal or polygonal with abundant granular eosinophilic cytoplasm and with central round nuclei and distant nucleoli. special stains like PTAH can be used to high light mitochondria

psammoma bodies, squamous cells, sebaceous and goblet cells may be present focally

Tyrosine rich crystals which are eosinophilic needle shaped or plate like are present either with in oncocytic cells or extracellularly

Areas of infarction and squamous metaplasia with atypical nuclei can also be seen

Variant

Clear cell oncocytoma

11% of oncocytomas has clear cells as predominant component

shows female predilection

clear cytoplasm is due to glycogen accumulation

These tumors have high frequency of bilaterality and recurrence

Differential diagnosis

Warthin tumor – Oncocytoma with lymphocytic infiltrate in stroma

Acinic cell carcinoma – similar cell arrangement and granularity in the cytoplasm but nuclei is peripherally located, in contrast to centrally located nuclei in oncocytoma