Placental alkaline phosphatase, PLAP

Placental alkaline phosphatase is a 70 kD membrane-bound alkaline phosphatase metalloenzyme, encoded by a gene on chromosome 2q. Its function is uncertain.

Immunohistochemical expression

• Various types of ovarian, testicular and extragonadal germ cell tumours:

  • seminoma

  • embryonal carcinoma

  • gonadoblastoma

  • yolk sac tumour

  • choriocarcinoma

  • intratubular germ cell neoplasia

  • not spermatocytic seminoma

  • not immature teratoma

• some carcinomas of

  • lung
    
  • gastrointestinal tract
    
  • ovary
    
  • endometrium

• skeletal and smooth muscle, and a range of tumour showing myogenic differentiation show cytoplasmic positivity for PLAP:

	Embryonal rhabdomyosarcoma	8/8 (>50% of cells staining in all cases)1
	Alveolar rhabdomyosarcoma	10/10 (>50% of cells staining: 8 cases, 10-50% of cells: 2 cases)1
	Leiomyoma - uterus	10/10 (>50% of cells staining in all cases)1
	Leiomyoma - soft tissue	1/1 (10-50% of cells staining)1
	Leiomyosarcoma - uterus	5/11 (>50% of cells staining: 1 case, 10-50% of cells: 4 cases)1
	Leiomyosarcoma - soft tissue	2/4 (>50% of cells staining: 1 case, 10-50% of cells: 1 case)1
	GIST	2/15 (>50% of cells staining in 2 cases. Positivity paralleled other markers of myogenic differentiation.)1
	Desmoplastic small round cell tumour	15/19 (>50% of cells staining in 6 cases, 10-50% of cells staining in 6 cases, <10% of cells staining in 3 cases. Tended to be dot-like paranuclear positivity. Positivity paralleled other markers of myogenic differentiation.)1
	Synovial sarcoma	1/9 (<10% of cells staining)1
	Wilm's tumour	1/8 (<10% of cells staining. Positivity paralleled other markers of myogenic differentiation.)1
	Myofibroblastic tumour	2/7 (one of three pulmonary inflammatory myofibroblastic tumours and one of two mammary myofibroblastomas. 10-50% of cells staining in one case, <10% of cells staining in 1 case)1
	Neurofibroma	0/101
	Schwannoma	0/101
	MPNST	0/61
	Traumatic neuroma	0/91
	Neuroblastoma	0/101
	Olfactory neuroblastoma	0/131
	Ganglioneuroblastoma	0/71
	Ganglioneuroma	0/11
	Fibrosarcoma	0/21
	Myxofibrosarcoma	0/21
	Low-grade fibromyxoid sarcoma	0/21
	Benign fibrous histiocytoma	0/41
	Dermatofibrosarcoma protuberans	0/111
	Fibromatosis	0/101
	Fibroma	0/31
	Nodular fasciitis	0/41
	Proliferative fasciitis	0/11
	Dermal scar	0/101
	Ewing's sarcoma/PNET	0/141
	Liposarcoma	0/111
	Glomus tumour	0/31
	Haemangiopericytoma	0/21
	Solitary fibrous tumour	0/21
	Small cell carcinoma	0/41
	Carcinoid tumour	0/61
	Paraganglioma	0/31
	Malignant mixed Mullerian tumour	0/11
	Carcinoma	0/71
	Malignant mesothelioma	0/11

Diagnostic utility

As a member of a panel for differentiating between trophoblastic tumour.

The differentiation of complete and partial molar pregnancies from choriocarcinoma

References

¹Goldsmith, J.D., Pawel, B., Goldblum, J.R., Pasha, T.L., Roberts, S., Nelson, P., Khurana, J.S., Barr, F.G. and Zhang, P.J. Detection and diagnostic utilization of placental alkaline phosphatase in muscular tissue and tumors with myogenic differentiation. Am J Surg Pathol 2002;26:1627-33.

This page last revised 9.1.2003.

©SMUHT/PW Bishop