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high grade PIN

Friday 16 November 2012

Definition: High grade PIN is characterized by a more uniform morphologic alteration. High-grade PIN consists of intermediate to large size preexisting glands with proliferative changes resulting in hyperchromatic appearance.

Cytologically, the acini and ducts are lined by malignant cells with a variety of architectural complexity and patterns. The individual cells are almost uniformly enlarged with increased nuclear/cytoplasmic ratio, therefore showing less variation in nuclear size than that seen in low grade PIN.

Many cells of HGPIN contain prominent nucleoli and most show coarse clumping of the chromatin that is often present along the nuclear membrane.

HGPIN can be readily appreciated at low power microscopic examination by virtue of the darker "blue" staining of the lining that reflects the expanded nuclear chromatin area.

High-grade PIN consists of intermediate to large size preexisting glands with proliferative changes resulting in hyperchromatic appearance. Note the small foci of cancer adjacent to PIN on the upper left and lower right.

Six variants of high-grade PIN have been described:
- tufted variant of high-grade PIN
- micropapillary variant of high-grade PIN

  • The acinar epithelial cells are arranged in long, delicate, finger-like structures in this micropapillary variant.

- flat variant of high-grade PIN

  • The acinar epithelial cells are pseudostratified and arranged linearly.
  • There is nuclear and nucleolar enlargement. Note the prominent apical snouts.

- cribriform variant of high-grade PIN

  • In cribriform high-grade PIN interconnecting bridges of acinar epithelial cells extend across the lumen of the glands.
  • Distinction of cribriform variant of high-grade PIN from adenocarcinoma may at times be extremely difficult.
  • Immunostain for high molecular weight cytokeratin 34bE12 may be useful in such cases – basal cell layer is fragmented in PIN and absent in adenocarcinoma.
  • The benign glands have continuous basal cell layer; high-grade PIN glands have fragmented basal cell layer; malignant glands completely lack basal cell layer.

- small cell variant of high-grade PIN
- inverted variant of high-grade PIN

Synopsis

- High-grade PIN consists of intermediate to large size preexisting glands with proliferative changes resulting in hyperchromatic appearance.
- enlarged nuclei
- prominent nucleoli
- residual basal cells.
- The acinar epithelial cells are pseudostratified and arranged linearly.
- There is nuclear and nucleolar enlargement.
- prominent apical snouts.
- intermediate-to-large size preexisting glands display nuclear and nucleolar enlargement and fragmented basal cell layer.