Thursday, 27 October 2011

Quiz






What does the development of an exophytic nodule on this naevus in the child patient, that has been present since birth, usually represent? Does the patched-hedgehog signalling pathway malfunction in this regard? What advice would you give the parent?



In this naevus, around puberty there is enlargement of the 
sebaceous glands, which are often located abnormally high in the 
dermis, with an increased number of closely set lobules and 
malformed ducts (A). A variety of appendageal tumours, sometimes
multiple, may develop within sebaceous naevi. The most commonly 
reported are trichoblastoma and syringocystadenoma papilliferum
(B). It should be noted that basaloid proliferations (arrow
that are seen in as many as half of all cases of naevus sebaceous
are not always easily differentiated from basal cell carcinoma
(BCC). Misinterpretation of trichoblastoma and basaloid
 proliferation as BCC has caused problems in the past.

How to differentiate between BCC and trichoblastoma 
pathologically?



Short and long answers are provided below as comments.

4 comments:

  1. Short answer:
    *Development of an exophytic nodule on a naevus sebaceous usually represents a benign appendageal tumour or viral wart.

    *There is no evidence of deregulated patched-hedgehog signalling pathway in trichoblastomas arising within naevus sebaceous. The late A. Bernard Ackerman used to stress that basal cell carcinoma surely may arise in naevus sebaceous of Jadassohn but the phenomenon is unusual and the vast majority of neoplasms diagnosed as basal cell carcinomas in naevus sebaceous of Jadassohn are trichoblastomas, and they are benign.


    *Excision of naevus sebaceous was common when these lesions were thought to carry an increased risk of basal cell carcinoma. Although the risk of development of malignancy exists, it is small. In adulthood, the patient can make an informed decision regarding removal.

    *Distinction can be difficult. Most BCCs provoke a round-cell inflammatory reaction of some degree. The presence of Merkel cells in trichoblastoma identified by immunohistochemical markers (cytokeratin 20, chromogranin) is useful in the differentiation from basal cell carcinoma which LACKS these cells. A further aid in the differential diagnosis between basal cell carcinoma and trichoblastoma is the immunohistochemical expression of androgen receptor. It is usually POSITIVE in basal cell carcinoma and negative in benign follicular neoplasms.

    ReplyDelete
  2. Long answer:
    1) Development of an exophytic nodule on a naevus sebaceous usually represents a benign appendageal tumour or viral wart. A variety of appendageal tumours, sometimes multiple, may develop within sebaceous naevi. The most commonly reported are trichoblastoma and syringocystadenoma papilliferum.


    2) There is no evidence* of deregulated patched-hedgehog signalling pathway in trichoblastomas arising within naevus sebaceous. The late A. Bernard Ackerman used to stress that basal cell carcinoma surely may arise in naevus sebaceous of Jadassohn but the phenomenon is unusual and the vast majority of neoplasms diagnosed as basal cell carcinomas in naevus sebaceous of Jadassohn are trichoblastomas, and they are benign. There are clear molecular differences between the basal cell carcinoma-like trichoblastomas arising in sebaceous naevi and true basal cell carcinomas. Basal cell carcinomas (BCCs) arise from pluripotential immature cells that form continuously during life, due to malfunctioning of the hedgehog-patched pathway (involved in embryonic tissue growth and organisation but when it malfunctions in adults it leads to neoplasia). Trichoblastoma is the benign counterpart of basal cell carcinoma and it should always be remembered that trichoblastoma has been misdiagnosed as basal cell carcinoma, the commonest malignancy reported in naevus sebaceous (of Jadassohn). Accordingly, some studies have overestimated the development of BCC in naevus sebaceous.



    *Takata M, Tojo M, Hatta N et al. No evidence of deregulated patched-hedgehog signaling pathway in trichoblastomas and other tumors arising within nevus sebaceus. J Invest Dermatol 2001; 117: 1666–70.





    3) Excision of naevus sebaceous was common when these lesions were thought to carry an increased risk of basal cell carcinoma. Although the risk of development of malignancy exists, it is small. In adulthood, the patient can make an informed decision regarding removal. Certainly demand for pathologic evaluation to evaluate for RARE malignancies exists, but excision should be considered on a case-by-case manner (with cosmetic reasons considered).



    4) Distinction can be difficult. Many basaloid proliferations are difficult to classify as a well-described entity. Most BCCs provoke a round-cell inflammatory reaction of some degree. The presence of Merkel cells in trichoblastoma identified by immunohistochemical markers (cytokeratin 20, chromogranin) is useful in the differentiation from basal cell carcinoma which LACKS these cells. A further aid in the differential diagnosis between basal cell carcinoma and trichoblastoma is the immunohistochemical expression of androgen receptor. It is usually POSITIVE in basal cell carcinoma and negative in benign follicular neoplasms.

    ReplyDelete
  3. Note that:


    *Organoid naevus (naevus sebaceous of Jadassohn) is a complex hamartoma involving not only the pilosebaceous follicle, but also the epidermis, and often other adnexal structures. In other words, this organoid naevus consists of a mixture of RELATIVELY normal-looking epidermis, dermis, sweat and sebaceous glands (skin as an organ). Syringocystadenoma papilliferum on the head and neck may be difficult to distinguish clinically from sebaceous naevus, although syringocystadenoma papilliferum tends to be pinker.


    * Epidermal naevus syndrome describes the association of sebaceous and/or verrucous naevi with other developmental defects, particularly of the central nervous system (CNS), eye and skeleton, first reported by Schimmelpenning in 1957 and by Feuerstein and Mims in 1962. Other authors have used the term Jadassohn’s naevus phakomatosis to describe this association. Although EARLY reports only included sebaceous naevi, the term is now used (modified definition) to include patients with verrucous naevi as well. More recently, some used the term ‘the epidermal naevus syndromes’ to include OTHER separate disorders, e.g.: Proteus syndrome, comedo naevus syndrome, child syndrome, and Becker’s naevus syndrome. This has created two difficulties: firstly, most dermatologists would not regard Becker’s naevus as an epidermal naevus; secondly, changing the meaning of ‘epidermal naevus syndrome’ leaves us without a name for the entity well established in the literature as ‘epidermal naevus syndrome’, none of the historical eponyms being satisfactory. Rook’s (textbook) maintains the ORIGINAL and well-established use of the term ‘epidermal naevus syndrome’ as ‘the association of sebaceous and/or verrucous epidermal naevi with other developmental defects, particularly of the CNS, eye and skeleton’. Having said so, epidermal naevus syndrome remains a heterogeneous group even in Rook’s (textbook) use, within which further conditions will be defined in the future. Eventually, when all the different mutations responsible for epidermal naevus syndrome have been defined, the term may become redundant (unnecessary).

    ReplyDelete
  4. Note that:

    Trichoblastomas are found—as is common with follicular tumours—on the head and neck (often within naevus sebaceous). Complete excision is often desirable as exclusion of a basal cell carcinoma may be difficult in small biopsies. Neither trichoblastomas nor basal cell carcinomas express hair keratins but citrulline can be demonstrated histochemically in some cases.

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Main Works of Reference List (The first eight are my top favourites)

  • British National Formulary
  • British National Formulary for Children
  • Guidelines (BAD - BASHH - BHIVA - Uroweb)
  • Oxford Handbook of Genitourinary Medicine, HIV, and Sexual Health
  • Oxford Handbook of Medical Dermatology
  • Rook's Textbook of Dermatology
  • Simple Skin Surgery
  • Weedon's Skin Pathology
  • A Concise Atlas of Dermatopathology (P Mckee)
  • Ackerman's Resolving Quandaries in Dermatology, Pathology and Dermatopathology
  • Andrews' Diseases of the Skin
  • Andrology (Nieschlag E FRCP, Behre M and Nieschlag S)
  • Bailey and Love's Short Practice of Surgery
  • Davidson's Essentials of Medicine
  • Davidson's Principles and Practice of Medicine
  • Fitzpatrick's Colour Atlas and Synopsis of Clinical Dermatology (Klaus Wolff FRCP and Richard Allen Johnson)
  • Fitzpatrick’s Dermatology in General Medicine
  • Ganong's Review of Medical Physiology
  • Gray's Anatomy
  • Hamilton Bailey's Demonstrations of Physical Signs in Clinical Surgery
  • Hutchison's Clinical Methods
  • Lever's Histopathology of the Skin
  • Lever's Histopathology of the Skin (Atlas and Synopsis)
  • Macleod's Clinical Examination
  • Martindale: The Complete Drug Reference
  • Oxford Handbook of Clinical Examination and Practical Skills
  • Oxford Textbook of Medicine
  • Practical Dermatopathology (R Rapini)
  • Sexually Transmitted Diseases (Holmes K et al)
  • Statistics in Clinical Practice (D Coggon FRCP)
  • Stockley's Drug Interactions
  • Treatment of Skin Disease: Comprehensive Therapeutic Strategies
  • Yen & Jaffe's Reproductive Endocrinology