Mohs

đź’ˇ
The smallest possible defect with maximum margin control
 
History
  • Frederic Mohs
  • In 1933, 23-year old research assistant Frederic E. Mohs was studying clinical reactions induced by different chemicals injected into cancerous rat tissues. He discovered that a zinc chloride solution could “fix” skin tissue suitability well for subsequent microscopic assessment while preserving full cyto-architectural structure of excised tissue
  • He then combined zinc chloride solution with stibnite and sanguinaria canadensis to develop a cohesive paste to be applied directly on skin cancer sites. Subsequent surgical excision did not cause any bleeding. Frozen sections could be then histologically prepared and viewed under the microscope.
  • Initially: called “chemosurgery”, took days to complete
  • 1930 - first concepts
  • 1941 - first publication
  • 1941 - official presentation
  • 1948 - technical developments
  • 1974 - fresh tissue technique (Stegman e ??)
  • 1977 - indication for melanoma as well
  • 1986 for sebaceous carcinoma of eyelid
  • 1988 for dermatofibrosarcoma protuberans
  • 1989 for fibrous histiocytoma and atypical fibrous xanthoma
  • 1997 for merkel cell carcinoma
  • 1980 - Antonio Picoto started to perform Mohs surgery in Lisbon (Portugal) aprendeu com Parry Robins
  • 1981 - Franscisco Camacho (Seville), Alejandro Camps Fresned (Barcelona), Julian Sancez Conejo Mir (Granada) started Mohs surgery in Spain
  • 1984-1986 Richard Mothery, Neil Walker, Christopher Zachary started in UK (Cardiff and London)
  • 1988 Helmut Breuninger started Tubingen Torte Technique (Germany)
  • 6-7 April 1990 in Estoril, Portugal, the European Society for Mohs Micrographic Surgery was started
Rational
  • Conventional excision histology
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    • 0,1% of margins examined
    • Mohs allows 100% margin control
  • Limitations of wide excision
    • 12-20% risk of local recurrence depending on histological subtype of the tumor
    • Delay between excison and pathology result
    • If flap was done, will need to be removed
    • Excess skin is excised
Advantages
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Indications
  • Basal Cell Carcinoma and Squamous Cell Carcinoma
    • Aggressive histologic subtypes
    • High risk locations (H-zone of the face)
    • Recurrent or large tumors
    • Immunosuppressed patients or radiation fields
    • Contraindicações:
      • Tumor muito grande
      • Estruturas extracutâneas envolvidas (ex. cartilagem)
  • Lentigo maligna
    • Higher cure rates (recurrence <2-5%)
    • Better cosmetic results
    • In guidelines - “mohs surgery is appropriate in complex anatomical sites is appropriate if imunohistochemistry available”
      • Tem que ser Slow Mohs para ter imunohistoquĂ­mica
  • Fibroxantoma AtĂ­pico e Sarcoma DĂ©rmico PleomĂłrfico
  • Dermatofibrosarcoma Protuberans
    • Tem que ser em slow mohs, porque tem menos falsos negativos e permite fazer CD34
  • Carcinoma Anexial MicroquĂ­stico
  • Paget Extramamário
    • Mas, mais recidivas porque muitas vezes multicĂŞntrico
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Técnicas de Cirurgia Micrográfica com controlo de margens
  • Slow Mohs | Mohs diferido
    • Amostra vai em formol → melhor qualidade
    • Permite fazer imunohistoquĂ­mica
    • Melanoma e dermatofibrosarcoma protuberans tĂŞm que ir desta forma, para ter menos falsos negativos
  • Mohs convencional
  • TĂ©cnica de Muffin
      • Frontiers | Muffin Technique Micrographic Surgery for Non-melanoma Skin Cancer Frontiers | Muffin Technique Micrographic Surgery for Non-melanoma Skin Cancer
      Figure 1. The principle of muffin technique micrographic surgery. The tumor is resected with a margin of healthy skin (A). The excised specimen is then incised 1–2 mm from the edge of the tissue block to form the lateral margins and ≅1 mm over the floor to form the deep margins (B). The central portion containing the tumor, the “muffin” itself, is removed (C)and the specimen is flattened to bring the lateral and deep margins, the “muffin paper,” into the same plane and color-coded for orientation (D). The histological sections are cut after being formaldehyde fixed and paraffin embedded in a horizontal direction starting from the bottom of the specimen. Of note, larger soft tumors can be curetted before excision, as is often practiced in mohs micrographic surgery. See also Supplementary Video 1.
      Figure 1. The principle of muffin technique micrographic surgery. The tumor is resected with a margin of healthy skin (A). The excised specimen is then incised 1–2 mm from the edge of the tissue block to form the lateral margins and ≅1 mm over the floor to form the deep margins (B). The central portion containing the tumor, the “muffin” itself, is removed (C)and the specimen is flattened to bring the lateral and deep margins, the “muffin paper,” into the same plane and color-coded for orientation (D). The histological sections are cut after being formaldehyde fixed and paraffin embedded in a horizontal direction starting from the bottom of the specimen. Of note, larger soft tumors can be curetted before excision, as is often practiced in mohs micrographic surgery. See also Supplementary Video 1.
  • Tubingen Torte Technique
      • Micrographic surgery according to the Tuebingen cake technique. The base and the margin of the tumor are assessed separately
      Micrographic surgery according to the Tuebingen cake technique. The base and the margin of the tumor are assessed separately
  • Munich Method
    • The Munich method differs in two points from the original description of fresh tissue MS technique. First, saucerization does not take place; the lateral and deep margins are not flattened into one plane before sectioning. Instead, serial horizontal cryostat sections are cut from the bottom up to the skin surface. Second, excision margins, therefore, are not cut at an angle of 45‡ but perpendicular to the skin surface.
Procedural Steps
  • Pre-Op Clinical Photographic time (Mohs 1)
    • Delinear o tumor visĂ­vel vlinicamente
  • Surgical Time (Mohs 2)
    • Shave of central tumor
    • Incision and nicks (12,6 and 3 o’clock)
    • Bevelling out the tumor
    • 50% of tumors are clear in the first stage
Histology Time (Mohs 3)
  • Sectioning and relaxation cuts to make sure the tissue lies flat
  • Staing the nicks with colors
  • Cryoembedding and sectioning
  • Staining
  • Microscopic examination
  • Analysis of complete surgical margin
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  • Pintar com cores nos bordos e na face profunda. Como se virou a amostra ao contrário as horas Sao inversas
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  • Cortar a amostra se necessário. Quantas mais amostras a analisar mais demorado. Cortar em 2 Ă© suficiente na maioria das vezes
  • Para amostras grandes: tĂ©cnica em que como a amostra Ă© muito grande se faz uma pequena incisĂŁo parcial em cima na epiderme para aplanar a amostra e bordo epidĂ©rmico ficar todo junto Ă  margem profunda
  • Comprimir a amostra numa chapa de metal fria (arrefecida com azoto lĂ­quido). Fazer força centrĂ­fuga de forma a que a epiderme fique no corte da margem profunda
  • Colocar no disco com a margem profunda que vai ser a primeira a ser seccionada para cima.
  • Colocar gel e comprimir com peso
  • Seccionar cortes de 5 micras. Para avançar em profundidade para a prĂłxima lâmina ficar mais profunda pode ser 20 micras
  • Para a gordura ficar bem pode se usar freeze spray
  • Se retirar a amostra do frios tato tem que se registar com lápis as 12 horas, para que depois os cortes tenham a mesma orientação ao colocar
  • Para tirar os cortes basta encostar a lâmina ao corte - usadas lâminas especiais com fixante
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  • TĂ©cnicas de coloração
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  • As amostras depois do corte se colocam em caixas em vĂŁo em formol para ser analisadas. SĂł nĂŁo sera possĂ­vel avaliar as margens, que já foram cortadas
  • Re-excision if necessary
  • Reconstruction Time
  • Post-Op Follow Up Time
 
  • Common indications and cure rates
  • Limitações
    • A cartilagem requer temperaturas mais altas que a pele para congelar (a pele ~-26 graus). Por isso Mohs na orelha nĂŁo resulta tĂŁo bem
 
  • Mohs diferido
    • Vai e formol, o que permite ver melhor queratinĂłcitos e melanĂłcitos
    • Usado em LM e lesões grandes (leiomiosarcoma por exemplo)
    • Dá-se ponto de aproximação entre as 6 e 9 horas
    • Vantagens
      • Gold standard for histological assessment
      • Recurrence rate 3-5%
    • Disadvantages
      • Histological processing takes 24-48h (in Italy up to a week)
      • Surgery is performed over several days
 
Criticisms to Mohs
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How to learn
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