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Animal-Type Melanoma – a Mini-Review Concern­ing One of the Rarest Variants of Human Melanoma


Melanom animálního typu – velmi vzácná varianta lidského melanomu

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Obdrženo: 17. 6. 2017

Přijato: 1. 11. 2018


Authors: L. Roncati 1;  F. Piscioli 2
Authors place of work: Department of Medical and Surgical Sciences, Institute of Pathology, University Hospital of Modena, Italy 1;  Provincial Health Care Services, Institute of Pathology, Santa Maria del Carmine Hospital, Rovereto, Italy 2
Published in the journal: Klin Onkol 2018; 31(6): 463-464
Category: Short Communication
doi: https://doi.org/10.14735/amko2018463

Summary

The authors declare they have no potential conflicts of interest concerning drugs, pro­ducts, or services used in the study.

The Editorial Board declares that the manu­script met the ICMJE recommendation for biomedical papers.

Submitted: 17. 6. 2017

Accepted: 1. 11. 2018

Described for centuries in the equines, especially gray horses, as “equine me­lanotic dis­ease”, it was later recog­nized in non-equine animal models and in humans, particularly on non UV-exposed skin. Animal-type melanoma, also known as pigmented epithelioid melanocytoma (PEM), is characterized by nodules and fascicles of epithelioid transformed melanocytes with pleomorphic nuclei and strik­ing pigmentation, dendritic cells, numerous melanophages and, sometimes, lymphocytic infiltrate [1,2]. Up-to-date, only small series have been reported in humans and, therefore, its bio­logical behavior remains unclear [3]. In 2010, Ludgate et al. examined the clinical behavior of 8 cases of equivocal and 14 cases of unequivocal PEM, conclud­ing that it shows a propensity for regional nodal metastases [4]. By systematic review and meta-analysis of the English literature, in 2015, Vyas et al. have identified 190 cases of PEM. The median Breslow depth was 3.8mm, loco-regional recurrence was found in 15 cases, recurrence with distant metastases in 6 cases and death occurred in 5 patients [5]. Recently, Bax et al. have suggested that the tumor follows an indolent clinical course, with very low risk of spread beyond regional lymph nodes [6]. Given the complexity of the matter, Elder and Murphy proposed a histological categorization of PEM and PEM-like lesions, with distinctive clinicopathological and bio­logic attitudes [7]. In this review, we briefly highlight the current information about this rare dis­ease.

Epithelioid blue nevus resembl­ing PEM

It is a hyperpigmented, poorly circum­scribed, dermal lesion, which shows heavily pigmented globular mela­no­cytes, intermingled with hypo­pig­­ment­ed spindle melanocytes. Commonly misinterpreted as classical blue ne­vus, in which markedly pig­mented, bipolar, spindled cells are associated with a host-derived fibroblastic react­ion, or as cellular blue nevus, a der­mal-hypo­dermic benign neoplasm characterized by an alveolar or fasci­cular pattern of growth sometimes with neuronevoid aspects, or as PEM (see later); its exact identification is important because it is strongly as­sociated with the Carney complex [8]. Conservative excision is generally recommended; moreover, affected patients (and their relatives) should be considered at risk for other diseases of the Carney complex, espe­cially cardiac myxoma [8].

PEM

Not associated with the Carney com­plex, it is quite similar to epithelioid blue nevus at scann­ing magnification, but cytological atypia and sparse low mitogenicity are encountered by a careful histological inspection, exactly as observable in melanocytic tumors of uncertain malignant potential (MELTUMP) [9–11]. When epidermal pa­getoid diffusion and overtly anaplastic nuclei are present, a dia­gnosis of malignant melanoma with prominent pigment synthesis can be also proposed [2]. Although the tumor can be lethal given the depth of invasion accord­ing to Magro et al., it seems to be less aggressive than other usual or unusual vertical growth phase melanomas [1,2]. Local lymph nodes are often involved by metastases – lymph node sentinel bio­psy is recommended and a wide re-excision (1–2cm margins) must be performed. Follow-up, as in any case of invasive malignant melanoma, should be conducted [2].

Tumoral melanosis mimick­ing PEM

It is a nodular cluster of melanophages, and it may represent a complete re­gression of a vertical growth phase melanoma or of a pigmented basal cell carcinoma [7]. In the radial and vertical growth phases, regression has negative impact on prognosis [12–16]; therefore, the follow-up should be very accurate since the lesion could be the result of a preceding, completely regressed melanoma [17–21].

A proper dia­gnostic fram­ing is crucial in these controversial cases and a good histology in the hands of an expert dermatopathologist remains the most reliable dia­gnostic start­ing point. Moreover, a loss of expression of cAMP-dependent protein kinase type I-alpha regulatory subunit, an enzyme encoded by the tumor-suppressor gene PRKAR1A, has been found in PEM, but not in common melanoma or other melanocytic lesions [22]. Therefore, it appears to have a great dia­gnostic value in help­ing to distinguish PEM from PEM-like lesions, which mimic the former histologically.

The authors declare they have no potential conflicts of interest concerning drugs, pro­ducts, or services used in the study.

The Editorial Board declares that the manu­script met the ICMJE recommendation for biomedical papers.

Submitted: 17. 6. 2017

Accepted: 1. 11. 2018

Dr. Luca Roncati, MD, PhD

Department of Medical and Surgical Sciences

Institute of Pathology

University Hospital of Modena

Policlinico

via del Pozzo, 71

I-41124 Modena, Italy

e-mail: emailmedical@gmail.com


Zdroje

1. Zembowicz A, Carney JA, Mihm MC. Pigmented epithelioid melanocytoma: a low-grade melanocytic tumor with metastatic potential indistinguishable from animal-type melanoma and epithelioid blue nevus. Am J Surg Pathol 2004; 28 (1): 31–40.

2. Magro CM, Crowson AN, Mihm MC. Unusual variants of malignant melanoma. Mod Pathol 2006; 19 (Suppl 2): 41–70. doi: 10.1038/modpathol.3800516.

3. Mandal RV, Murali R, Lundquist KF et al. Pigmented epithelioid melanocytoma: favorable outcome after 5-year follow-up. Am J Surg Pathol 2009; 33 (12): 1778–1782. doi: 10.1097/PAS.0b013e3181b94f3c.

4. Ludgate MW, Fullen DR, Lee J et al. Animal-type melanoma: a clinical and histopathological study of 22 cases from a single institution. Br J Dermatol 2010; 162 (1): 129–136. doi: 10.1111/j.1365-2133.2009.09271.x.

5. Vyas R, Keller JJ, Honda K et al. A systematic review and meta-analysis of animal-type melanoma. J Am Acad Dermatol 2015; 73 (6): 1031–1039. doi: 10.1016/j.jaad.2015.08.016.

6. Bax MJ, Brown MD, Rothberg PG et al. Pigmented epithelioid melanocytoma (animal type melanoma): an institutional experience. J Am Acad Dermatol 2017; 77 (2): 328–332. doi: 10.1016/j.jaad.2017.01.029.

7. Elder DE, Murphy GF. Melanocytic tumors of the skin. AFIP atlas of tumor pathology. 4th ed. Washington, DC: American Registry of Pathology 2010.

8. Carney JA, Ferreiro JA. The epithelioid blue nevus. A multicentric familial tumor with important associations, including cardiac myxoma and psammomatous melanotic schwannoma. Am J Surg Pathol 1996; 20 (3): 259–272.

9. Piscioli F, Pusiol T, Roncati L. Diagnostic approach to melanocytic lesion of unknown malignant potential. Melanoma Res 2016; 26 (1): 91–92. doi: 10.1097/ CMR.0000000000000215.

10. Roncati L, Piscioli F, Pusiol T. SAMPUS, MELTUMP and THIMUMP – diagnostic categories characterized by uncertain biological behavior. Klin Onkol 2017; 30 (3): 221–223. doi: 10.14735/amko2017221.

11. Piscioli F, Pusiol T, Roncati L. Diagnostic disputes regarding atypical melanocytic lesions can be solved by using the term MELTUMP. Turk Patoloji Derg 2016; 32 (1): 63–64. doi: 10.5146/tjpath.2015.01330.

12. Roncati L, Piscioli F, Pusiol T. The significance of regression in thin melanoma of the skin. Ir J Med Sci 2018; 187 (1): 95–96. doi: 10.1007/s11845-017-1612-1.

13. Roncati L, Piscioli F, Pusiol T. Sentinel lymph node in thin and thick melanoma. Klin Onkol 2016; 29 (5): 393–394.

14. Roncati L, Piscioli F, Pusiol T. Current controversies on sentinel node biopsy in thin and thick cutaneous melanoma. Eur J Surg Oncol 2017; 43 (2): 506–507. doi: 10.1016/j.ejso.2016.09.014.

15. Piscioli F, Pusiol T, Roncati L. Wisely choosing thin melanomas for sentinel lymph node biopsy. J Am Acad Dermatol 2017; 76 (1): e25. doi: 10.1016/j.jaad.2016.08.069.

16. Piscioli F, Pusiol T, Roncati L. Higher predictive value of sentinel lymph node biopsy in patients with histological subcategorization of thin melanoma. Int J Dermatol 2017; 56 (5): e93–e94. doi: 10.1111/ijd.13548.

17. Roncati L, Piscioli F, Pusiol T. Surgical outcomes reflect the histological types of cutaneous malignant melanoma. J Eur Acad Dermatol Venereol 2016; 31 (6): e279–e280. doi: 10.1111/jdv.14023.

18. Piscioli F, Pusiol T, Roncati L. Critical points of T1 stage in primary melanoma. Melanoma Res 2017; 27 (4): 399. doi: 10.1097/CMR.0000000000000357.

19. Piscioli F, Pusiol T, Roncati L. Nowadays a histological sub-typing of thin melanoma is demanded for a proper patient management. J Plast Reconstr Aesthet Surg 2016; 69 (11): 1563–1564. doi: 10.1016/j.bjps.2016.08.026.

20. Roncati L, Pusiol T, Piscioli F. Thin melanoma: a generic term including four histological subtypes of cutaneous melanoma. Acta Dermatovenerol Croat 2016; 24 (4): 169–174.

21. Piscioli F, Pusiol T, Roncati L. Thin melanoma subtyping fits well with the American Joint Committee on Cancer staging system. Melanoma Res 2016; 26 (6): 636. doi: 10.1097/CMR.0000000000000301.

22. Zembowicz A, Knoepp SM, Bei T et al. Loss of expression of protein kinase a regulatory subunit 1alpha in pigmented epithelioid melanocytoma but not in melanoma or other melanocytic lesions. Am J Surg Pathol 2007; 31 (11): 1764–1775. doi: 10.1097/PAS.0b013e318057faa7.

Štítky
Paediatric clinical oncology Surgery Clinical oncology

Článok vyšiel v časopise

Clinical Oncology

Číslo 6

2018 Číslo 6
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